Various assemblies for providing (vertical) support while permitting (lateral) movement of doors are known in the art. Such assemblies have been utilized for elevator cab and hoistway door panels, doors on railway freight cars, as well as other types of slidable doors. The present invention is useful in many types of slidable doors, but will be described herein with reference to elevator doors for which it is particularly useful
Conventional sliding door assemblies typically comprise a door track, a door hanger, a hanger sheave and an upthrust roller. The door hanger is a support which is typically fastened to the upper portion of a door panel, and which supports and allows the sliding movement, e.g. horizontally, of the door panel. The hanger sheave typically comprises a wheel or roller that is connected to a door panel by the door hanger. The door track is a rail which accepts the rolling assembly of door hanger and allows the horizontal sliding movement required to open and close the doors. An upthrust roller is a roller bearing installed onto an eccentric shaft and mounted on the door hanger for limiting the (vertical) motion of a (horizontally) sliding door panel to keep the panel from lifting off the door track.
One such type of conventional elevator door assembly known in the art is shown in FIG. 1 wherein an elevator cab or hoistway door panel 10 (hereinafter the door panel) is slidably supported on door track 50 via door hanger 20. A hanger sheave (roller) assembly 30 is rotatably mounted on door hanger 20. Hanger sheave assembly 30 is designed to receive projecting portions 51 of door track 50. Though not shown in FIG. 1, door track 50 is securely mounted such that it can support door panel 10. To prevent the hanger sheave assembly 30 from jumping off door track 50 when the elevator door 10 is jolted by mechanical means or by people moving equipment onto or out of the elevator, the conventional design incorporated an upthrust roller 40 mounted on door hanger 20. The upthrust roller 40 is conventionally placed slightly below and in close proximity to, for example, 0.020-0.030 inches, door track 50. Thus, in normal operation, hanger sheave assembly 30 rolls along door track 50 and projections 51 and upthrust roller 40 only contacts projections 51 if the elevator door 10 is jolted. Upthrust roller 40 is conventionally eccentrically mounted on door hanger 20 via adjustable mount 45 in a manner which permits the adjustment of the gap between upthrust roller 40 and door track 50.
The traditional assembly containing a track, hanger, hanger sheave and upthrust roller has provided fairly good service through the years. However, one inherent problem still exists. This problem is caused by the wearing of the hanger sheave 31 and its effect upon the critical relationship between the upthrust roller 40 and track 50. For example, as the hanger sheave 31 wears, a gradual but substantial clearance will develop between the underside of the door track 50 and the upthrust roller 40. If a periodic re-adjustment is not performed to the upthrust roller 40, the hanger sheave assembly 30 may easily jump off of the track 50. This often occurs when the door panels 10 are struck by mechanical means or by person moving equipment on or out of the elevators.
Another disadvantage of the conventional design shown in FIG. 1 is that since hanger sheaves are typically formed of synthetic materials such as nylon or another plastic material which may readily melt in the event of a fire, the door panel 10 could easily become stuck thereby trapping the occupants in the elevator.
Another known design for a door hanger is shown in U.S. Pat. No. 807,141, to J.J. Tatum, patented Dec. 12, 1905. That design incorporates two rollers, C C, which are positioned about a rail 1. That patent does not disclose the desirability of adjusting the bottom roller and lacks the advantages of the present invention described below.
Another known assembly is disclosed in U.S. Pat. No. 1,024,502, to P.M. Elliott, patented Apr. 30, 1912, which discloses a door mechanism for a railway freight car and antifriction roller F which rests upon the upper face of a track flange b.sup.2 and a small roller F' positioned below the track flange.
Another sliding door assembly is shown in Patentschrift, No. 964,030, dated May 16, 1957. From the figures of this Patentschrift, it is apparent that this design utilizes rollers within a rail but does not disclose the use of upthrust rollers. With reference to FIG. 4, it will be appreciated that the two rollers 123 and 223 each support different elements 113 and 213, respectively.
Still another known arrangement is disclosed in U.S. Pat. 4,120,072, to M. Hormann, patented Oct. 17, 1978, for a COMBINED SUPPORTING ROLLER-FRICTION DRIVE ARRANGEMENT FOR OVERHEAD SINGLE-PANEL DOORS. This design is somewhat similar to that described above with reference to prior art FIG. 1 wherein a roller 6 rides on a running track 8, however in this design, counterpressure rollers 12 contact the underside 13 of running track 8. Counterpressure rollers 12 are provided with an adjusting means 16 permitting the adjustment of the counterpressure rollers 12 in the direction toward the running track 8. In accordance with this design, at least one of the counterpressure rollers 12 is always in contact with the bottom side 13 of the running track 8. (see column 3, lines 49-55)
It will be appreciated that the known sliding door assemblies which utilize an upthrust roller in close proximity to the track require continual maintenance to ensure that the gap between the upthrust roller and door track does not become so great that the hanger sheave can be jolted off the track. The other designs which place the track assembly in continuous contact with an upthrust roller result in the wearing down of not only the hanger sheave but also the upthrust roller and, if the upthrust roller is formed of a metal such as steel, may cause an irritating noise during use.